Staple fibres yarn processing

Yarn produced by the Lilienfeld process lacked sufficient elasticity to make it attractive for textile purposes but it has been used to make a particularly strong staple fibre under the name of Durafil. This fibre has a dry tenacity of 3-7 to 4-1 g per den, compared with 2-54 for conventional viscose staple and a wet tenacity of 2-73 to 3T compared with 1-53. 

The dimensional stabUity of synthetic yarns and textiles can be considerably enhanced by a thermosetting process, i.e. heat treatment under dry heat, steam or hot water. Thermosetting may be undertaken either with or without applied tension. Thermally treated filament yarns and staple fibres show less heat shrinkage, have a reduced tendency to crimp and show improved recovery from creasing. 

As some reverse air filters also employ shake or vibration mechanisms, it is not uncommon to find the same fabric in both types of filter. This notwithstanding, conventional reverse air filter sleeves are most likely to feature multifllament yarns in the warp combined with staple fibre yams in the weft. On this occasion the twill weave will be replaced by a 5- or 6-shaft warp satin construction, which is designed to facilitate superior dust release from the smooth multifilament warp yarns during the less aggressive cleaning phase. Particle capture will be further enhanced if the fabric is subjected to a raising or napping process on the reverse side. A typical polyester construction, as may be found in a reverse air filter, is also shown in Table 7.3 for comparison with the previous construction. 

The tensile strength of wool fibres is important because the fibres are subject to severe forces during the initial stages of processing, when the fleeces are cleaned and the fibres are separated into forms that can be spun into yarn. The strength of wool is commonly tested as the staple strength , which involves all the complications of load... 

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